1. Field of the Invention
The present invention relates, generally, to a recording thin film magnetic head used as, for example, a flying magnetic head or the like and, more particularly, to a thin film magnetic head that is capable of appropriately decreasing side fringing, and that can be manufactured with high reproducibility, and a method of manufacturing the same.
2. Description of the Related Art
FIG. 24 is a partial front view showing the structure of a conventional thin film magnetic head (inductive head), and FIG. 25 is a partial cross-sectional view of the thin film magnetic head shown in FIG. 24.
In FIGS. 24 and 25, reference numeral 1 denotes a lower core layer made of a magnetic material such as permalloy or the like, with insulation layers 3 formed on both sides of the lower core layer 1. As shown in FIG. 24, a gap layer 4 and an upper pole layer 5 are formed with track width Tw on the lower core layer 1 to be exposed in the surface facing a recording medium. The gap layer 4 is formed to extent along the top of the lower core layer 1 to the position of contact between the lower core layer 1 and the base end 10b of an upper core layer 10 which will be described below, as shown in FIG. 25. On the other hand, the upper pole layer 5 is formed to extend to the top of a Gd determining layer 6 formed on the gap layer 4. The gap layer 4 is made of a nonmetallic insulating material, for example, SiO2 or the like.
As shown in FIGS. 24 and 25, an insulation layer 7 is formed on both sides of the upper pole layer 5 in the track width direction (the X direction shown in the drawings) and on the back side in the height direction (the Y direction shown in the drawings). Furthermore, a coil layer 13 is patterned in a spiral shape on the insulation layer 7, and an insulation layer 9 made of an organic insulating material is formed on the coil layer 13 to cover the coil layer 13.
The upper core layer 10 is formed on the insulation layer 9, for example, by a frame plating method so that the front end 10a of the upper core layer 10 is magnetically connected to the upper pole layer 5 and exposed in the surface facing the recording medium. The base end 10b of the upper core layer 10 is magnetically connected to the lower core layer 1.
As shown in FIG. 24, the entire front surface 10c of the upper core layer 10 is exposed in the surface facing the recording medium.
Next, the method of manufacturing the thin film magnetic head shown in FIGS. 24 and 25 will be described below with reference to FIGS. 26 to 32. As shown in FIG. 26, the gap layer 4 made of an insulating material, for example, SiO2 is formed over the entire surface of the lower core layer 1, and a resist layer 11 having a trench 11a having the track width Tw is formed on the gap layer 4. The trench 11a is formed with the predetermined length dimension from the surface facing the recording medium in the height direction (the Y direction shown in the drawing). Then, the upper pole layer 5 made of, for example, a NiFe alloy, is formed in the trench 11a by plating, and the resist layer 11 is removed.
As shown in FIG. 27, the width dimension of the upper pole layer 5, i.e., the track width Tw, is, for example, 0.45 xcexcm, and the height dimension is about 3.5 to 3.8 xcexcm. In FIG. 27, both sides of the upper pole layer 5 in the track width direction (the X direction shown in the drawing) are etched by ion milling (trimming step). As shown in FIG. 28, the portions of the gap layer 4 which protrude from the width dimension of the upper pole layer 5 in the track width direction are removed by the ion milling, and portions of the upper surface of the lower core layer 1 on both sides of the upper pole layer 5 are also removed to form a protrusion 1b and inclined surfaces 1a at the top of the lower core layer 1.
In FIG. 29, the insulation layer 7 of Al2O3 or the like is formed to cover both sides of the upper pole layer 5 and the upper pole layer 5 on the lower core layer 1, and polished to line Axe2x80x94A by a CMP technique or the like. FIG. 30 shows the state after polishing.
Next, the coil layer 13 and the insulation layer 9 shown in FIG. 25 are formed on the insulation layer 7, and then a resist layer 12 is formed on the insulation layers 7 and 9, and the upper pole layer 5, as shown in FIG. 31 (partial plan view). Then, a patterned portion 12a of the resist layer 12 is exposed and developed to remove the patterned portion 12a. 
Then, a magnetic material is plated in the patterned portion 12a, and the resist layer 12 is removed to complete the upper core layer 10. FIG. 32 shows the structure of the tip portion of the thin film magnetic head.
The trimming step is usually carried out twice, the first trimming step comprising ion irradiation at an angle as close to a right angle as possible with the film plane direction of the lower core layer 1. In this step, the portions of the gap layer 4 on both sides of the bottom of the upper pole layer 5 are removed, and the lower core layer 1 formed below the gap layer 4 is also partially removed to form the protrusion 1b on the lower core layer 1. This step causes a problem in which the magnetic powder produced by cutting the gap layer 4 and the lower core layer 1 again adheres to the sides of the upper pole layer 5. Therefore, the second trimming step comprises ion irradiation in a direction more inclined that that in the first trimming step to remove the magnetic powder and, at the same time, to form the inclined surfaces 1a at the top of the lower core layer 1 on both sides of the upper pole layer 5.
However, in the structure of the thin film magnetic head shown in FIGS. 24 and 25, the front end surface 10c of the upper core layer 10 having a width dimension larger than the track width Tw is exposed in the surface facing the recording medium, and thus side fringing occurs due to a magnetic leakage between the upper core layer 10 and the upper pole layer 5, thereby causing the problem of decreasing the area recording density due to the occurrence of side fringing. Therefore, in order to manufacture a thin film magnetic head adaptable to a higher recording density in future, it is necessary to decrease the track width Tw and the occurrence of side fringing.
The method of manufacturing the thin film magnetic head shown in FIGS. 24 and 25 comprises the trimming step which causes variations in the track width Tw and the shape, and the problem of significantly decreasing the height of the upper pole layer 5. The reason for performing the trimming step is that in the state shown in FIG. 27, the gap layer 4 and the lower core layer 1 are formed to extend on both sides of the bottom of the upper pole layer 5, thereby easily causing the occurrence of side fringing between the upper pole layer 5 and the lower core layer 1. In the trimming, as shown in FIG. 28, the portions of the gap layer 4 which extend on both sides of the bottom of the upper pole layer 5 are removed, and the protrusion 1b and the inclined surfaces 1a are formed in the lower core layer 1 to increase the distance between the upper pole layer 5 and the lower core layer 1, whereby the occurrence of side fringing can be possibly appropriately decreased.
However, the trimming step causes a variation in the amount of the magnetic powder adhering to both sides of the upper pole layer 5 and a variation in removal of the magnetic powder, and a significant decrease in the height of the upper pole layer 5 because the first trimming step comprises ion irradiation in the direction as close to a right angle as possible with the film plane direction of the lower core layer 1. As a result, variations easily occur in the track width Tw and the shape of the upper pole layer 5, and the height dimension of the upper pole layer 5 is significantly decreased to cause a variation in the height dimension. Therefore, the trimming step deteriorates the reproducibility of the manufacture of the thin film magnetic head, and the volume of the upper pole layer 5 is decreased due to a decrease in the height dimension thereof, thereby easily bringing the upper pole layer 5 into a magnetic saturation state and deteriorating recording performance.
The present invention is aimed at solving the above problems of conventional thin film magnetic heads, and an object of the present invention is to provide a thin film magnetic head and a method of manufacturing the same which can appropriately prevent side fringing, and which can be manufactured with high reproducibility.
A thin film magnetic head of the present invention comprises a lower core layer, a recording core exposed at a face surface facing a recording medium and comprising one of (1) a lower pole layer, a gap layer and an upper pole layer, or (2) a gap layer and an upper pole layer, which are laminated in turn on the lower core layer. An upper core layer is magnetically connected to the upper pole layer of the recording core. A coil is provided for inducing a recording magnetic field in the lower core layer, the recording core and the upper core layer, wherein the front end surface of the upper core layer, which faces the recording medium side, has the shape of a curved surface so that the front surface gradually retreats in a height direction that is generally perpendicular to the face surface as it approaches both sides thereof in a track width direction that is generally parallel to the face surface.
In the present invention, the front surface of the upper core layer is formed in the shape of a curved surface so that the front surface gradually retreats in the height direction as it approaches both sides thereof in the track width direction. Therefore, unlike the conventional thin film magnetic head, the front surface of the upper core layer is not entirely exposed at the face surface, whereby the occurrence of side fringing can be appropriately prevented.
In addition, since the front surface of the upper core layer is formed in the shape of a curved surface in the track width direction, the occurrence of side fringing can be decreased as compared with the conventional thin film magnetic head even when the upper core layer is patterned on the upper pole layer at a position offset from a predetermined position with respect to the upper pole layer.
In the present invention, a line tangent to each of both termination points of the curved surface in the track width direction form an angle with the track width direction is preferably about 30xc2x0 to about 60xc2x0.
The upper core layer preferably comprises a front region which extends in the height direction from the termination points of the curved front surface, and which has a constant width dimension in the track width direction. The upper core layer further includes a back region in which the width dimension in the track width direction gradually increases in the height direction from the termination points of the front region.
The front surface of the upper core layer may be located at a position displaced away from the face surface in the height direction. In this case, the front surface of the upper core layer is not exposed at the face surface.
Furthermore, as described above, the because front surface of the upper core layer is displaced away from the face surface in the height direction, the occurrence of side fringing can be prevented.
In the above-mentioned construction, the minimum distance L3 from the face surface to the front surface of the upper core layer is preferably smaller than the maximum length dimension of the recording core in the height direction from the face surface. The distance L3 is preferably about 0 xcexcm less than L3xe2x89xa6 about 0.8 xcexcm.
In the present invention, at least a portion of the front surface of the upper core layer may be located at the face surface. In the present invention, as described above, the front surface is formed in the shape of a curved surface so that the front surface gradually retreats in the height direction as it approaches both sides thereof in the track width direction. Therefore, unlike in the conventional thin film magnetic head, the front surface is only partially exposed in the face surface instead of entirely exposed.
In the construction of the present invention, the front surface of the upper core layer is preferably formed in a curved surface or an inclined surface so that the thickness of the upper core layer gradually increases in the height direction from the lower core layer side to the upper core layer side. In this way, the front end surface of the upper core layer is formed in a curved surface or an inclined surface so that the thickness of the upper core layer gradually increases in the height direction, thereby further decreasing the occurrence of side fringing, and facilitating a flow of a magnetic flux from the upper core layer to the upper pole layer. Therefore, a thin film magnetic head can be made with improved recording performance.
In the present invention, the upper core layer has a back surface that is located at a position behind the front end surface in the height direction, and that is formed in a curved surface or an inclined surface, such that the thickness between the lower core layer and the upper core layer gradually increases in the height direction.
Assuming that the inclination angle xcex81 of the inclined surface formed in the back surface with respect to the height direction, or the inclination angle of a line tangent to the curved surface at an intermediate point between with a termination point at the magnetic core and with respect to the height direction a termination point at an underside of the upper core layer, and that the inclination angle xcex82 of the inclined surface formed as the front surface of the upper core layer with respect to the height direction, or the inclination angle of a line tangent to the curved surface at an intermediate point between a termination point at the magnetic core and a termination point at the upper surface of the upper core layer with the height direction, xcex82 is preferably larger than xcex81.
In this construction, a magnetic flux from the upper core layer can be efficiently caused to flow to the upper pole layer to permit an attempt to improve the recording performance. The inclination angle xcex82 is preferably about 60xc2x0xe2x89xa6xcex82 less than  about 90xc2x0.
In the present invention, the width dimension of the end of the upper core layer, which is connected to the upper pole layer, in the track width direction is preferably larger than the width dimension of the upper pole layer in the track width direction. This construction permits an efficient flow of a magnetic flux from the upper core layer to the upper pole layer, thereby permitting an attempt to improve the recording performance.
In the present invention, the recording core preferably comprises a front region that extends from the face surface in the height direction and that has a constant width dimension in the track width direction, and a back region in which the width dimension in the track width direction gradually increases in the height direction beginning from a terminal portion of the front region By forming the back region having a larger track width Tw, the contact area between the recording core and the upper core layer can be increased.
The upper core layer is preferably connected to at least the back region of the recording core so that a magnetic flux from the upper core layer can be efficiently caused to flow to the upper pole layer.
In the present invention, the gap layer is preferably made of a platable nonmagnetic metal material. In this case, as the nonmagnetic metal material, at least one material is preferably selected from NiP, NiPd, NiW, NiMo, Au, Pt, Rh, Pd, Ru, and Cr. A method of manufacturing a thin film magnetic head having a face surface that faces a recording medium comprising the steps of:
(a) carrying our a process of one of (1) sequentially laminating in turn a lower pole layer, a gap layer and an upper pole layer such that a lateral dimension of the lower pole layer and the upper pole layer in a track width direction, wherein the track width direction is a direction substantially parallel to the face surface is determined at the face surface, or (2) sequentially laminating in turn a gap layer and an upper pole layer such that the lateral dimension of the upper pole layer in the track width direction is determined at the face surface, to form a recording core;
(b) before or after step (a) forming an insulation layer around the recording core, and grinding the insulation layer so that the upper surfaces of the recording core and the insulating lay lie in substantially the same plane;
(c) forming a resist layer on the recording core and the insulation layer;
(d) forming an upper core layer pattern for in the resist layer such that a front surface of the upper core layer pattern is in proximity to the face surface and has a curved surface which gradually retreats in the height direction as it approaches side surfaces of the upper core layer pattern in the track width direction; and
(e) plating a magnetic material in the pattern to form the upper core layer having a curved front surface conforming to the upper core layer pattern.
In the present invention, step (d) comprises exposing a portion of the resist layer other than the upper core layer pattern and developing the portion to form one of an inclined surface or a curved surface at the front surface of the upper core layer pattern, such that the front surface gradually retreats in the height direction as it approaches a top surface thereof, and which is partially located at the same position as the face surface.
In the step (e), at least a portion of forming an inclined surface or curved surface at the front surface of the upper core layer such that at least a portion of the front surface is located at the face surface, and the front end surface gradually retreats in the height direction as it approaches an upper surface of the upper core layer in the track width direction.
In the present invention, the gap layer is preferably made of a platable nonmagnetic metal material. Specifically, the nonmagnetic metal material comprises at least one material preferably selected from the group consisting of NiP, NiPd, NiW, NiMo, Au, Pt, Rh, Pd, Ru, and Cr.
The manufacturing method of the present invention can manufacture a thin film magnetic head with high reproducibility and little variation in the track width Tw and height dimension of the recording core, and can easily form a thin film magnetic head capable of suppressing the occurrence of side fringing.
In exposure and development of the resist layer used for forming the pattern of the upper core layer, the portion of the resist layer other than the pattern is irradiated with light and then developed to form the inclined surface or curved surface at the front surface of the pattern. The front surface gradually retreats in the height direction as it approaches the top thereof. As a result, the front surface of the upper core layer formed in the pattern can be formed as an inclined surface or curved surface, so that the thickness of the upper core layer increases in the height direction as it approaches the top the upper core layer.